Method for producing photographic reproductions in color



Sept 49 l934 L. G. NlcoLL 1,972,311

METHOD FOR PRODUGING PHOTOGRAPHIC REPRODUCTIONS IN COLOR -Filed July 25, 1951 2 Sheets-Sheet l maar" Invenor. Leonard G. Nicoll bya/ Ays,

Sept. 4, 1934. L. G NIQOLL 1,972,311

METHOD FOR PRODCING PHOTOGRAPHIC REPRODUCTIONS IN COLOR Filed July 25, 1931 2 Sheets-Sheet 2 /2'2 F l G. 5. 25 m (l q1?, l 4 W 52 FI G. [25

B Fl G. 3. @j KVM c A C 42 Inventor. Leonard G. Nicol! bymwkw Patented Sept. 4, 1934 UNITED STATES :METHOD FOR PRODUCING PHOTGRAPHIC REPRODUCTIONS IN COLOR Leonard G. Nicoll, Boston, Mass.

Application July 25, 1931, Serial No. 553,081

-13 Claims.

This invention relates to improvements in methods and apparatus for making photographic reproductions in natural colors.

In the art of photography every step forward has been toward the goal of perfect realism. In this progress the development of a practical method of producing prints in natural color has met with a great deal of diiiculty. This fact is borne out by appreciating the fact' that a great deal more activity has taken place in the development of reproductions in monochrome. No matter how perfectly the tones of a subject are rendered without color the results are at best only approximately accurate reproductions. The importance and desirability of reproducing in color has always been recognized since the realization of true and accurate reproduction could never be attained in any medium but that of color. The failure of existing methods to faithfully reproduce in color, and the failure to produce a method commercially workable has undoubtedly prevented its more universal adoption.

The object of the present invention is to provide a method and apparatus for producing a multiplicity of colored photographic reproductions in which the method may be carried out by one who is not highly skilled, and in which the material employed is always in such physical condition as to be readily handled or treated chemically without fear of injury.

A further object` of the invention is to provide a method o f producing multi-color photographic reproductions in which every color of which the subject is composed and the black and white which appear in the subject are faithfully reproduced.

A further object of the invention is to provide a process in whch the final color reproduction contains two or more elements bearing the funda- 40 mental colors of the subject, each of which may be worked readily upon and modified t6 produce a desired result in the finished reproduction.

In the drawings:

Fig. 1 is a cross sectional View of a transparency in natural color.

Fig. 2 is a cross sectional view of an apparatus for selectively projecting three beams of color representing the fundamental colors`of nature upon a printing frame.

Fig. 3 is a cross sectional view through three photographically' sensitized elements bearing a panchromatic emulsion.

Fig. 4 is a cross section through three sheets of silver bromide sensitized printing paper of special 55 construction.

Fig. 5 is a cross section of one of the bromide sheets with its emulsion adhering to a temporary support.

Fig. 6 is a cross section through a steaming apparatus used in the process. 60

Fig. 7 is a cross section-on line '7-7 Fig. 6.

Fig. 8 is a cross section similar to that shown in Fig. 5 with the paper backing'of the bromide sheet removed.

Fig. 9 is a cross section of the finished picture 35 mounted upon a support.

The present invention presents a thoroughly practical method of making accurate full color reproductions photographically. The process makes possible the production of a multiplicity of identical reproductions, and may .be carried out upon a commercial quantity production basis.

In order to emphasize the importance and far reaching possibilities of such a process, itis well to discuss the relative characteristics of the multicolor processes as compared to monochromatic representations which are now so commonly in use.

Monochromatic photography has been so prevaient that the absence of color has not been missed S0 by the general public, but once colored photography has been established on a practical commercial basis, monochrome prints will lose much of their present day popularity.

The process comprising the present invention may be adapted readily to making multi-color reproductions by employing two or more fundamental colors. Avery satisfactory two color reproduction may be produced. The better quality resulting from the use of three or four fundamental colors warrants the additional labor and materials necessary for such a reproduction. The partcula-n embodiment of the invention herein described will involve the use of three fundamental colors, such, for instance, as the red, the

A fundamental colors in the subject, however, maybe obtained by means of various other processes, such as obtaining the appropriate number of negative records by exposure through trichrome lters directly from the subject in which case three separate exposures must be made through a lens or an especially constructed camera must be used which projects images containing the three standard colors upon three separate plates or other panchromatic material.

By the preferred method, however, the color transparency above referred to is used as a basis from which to produce the nal reproduction. Three negative records are made upon appropriate panchrornatically sensitized material. Each negative record thus made bears an image representing the amount and position of one of the fundamental colors which appear in the subject.

A convenient means for obtaining these records is by the use of the apparatus disclosed in Fig. 2. The apparatus is mounted preferably upon a bench or table 1 in which anopening 2 is formed substantially of the same shape and area as the color plate used in the process. A printing frame 3 is placed over the opening 2 in which are received .he materials employed in this step of the process. Below the opening 2 is secured a light tight casing 4 upon the lower end of which is secured a frame 5 having a slot 6 therein in which 4is slidably received a color filter carrying frame '7 which is movable within the slot 5 in a direction parallel to the printing frame 3. Below the frame 5 is secured another frame 8 in which is received an additional color filter. Below the frame 8 is located a light tight chamber 9 containing a light source 10. v

To produce the desired negative records, a compensating filter 11 is placed desirably in the frame 8 which acts to out off a particular part of the spectrum emanating from the light source which is undesirably strong. A set of colored filters then are placed in slots 12, 13 and 14 within the frame 7. These filters preferably are standard trichromatic. The blue lter 15 is placed in the slot 12, the red lter 16 is placed in the slot 13, and the green lter 17 is placed in the slot 14. The particular -arrangement of the lters is immaterial however. As shown in the drawing the filter 15 is in position to intercept the light passing from the light source to the printing frame in which is placed the transparency 18 from which the reproduction is to be made. This beam of blue light passes through the transparency and strikes a panchromatically sensitized sheet 19 placed in contact with the transparency, and produces when developed a negative record thereon of that color contained in the transparency complementary to the blue of the lter 15, such complementary color being the yellow. A negative record is made in the same way of the blue and the red contained in the transparency upon separate sensitized sheets by moving the filters 16 and l'lrespectively in the position occupied by the lter 15 in the drawings. The records made of the blue and the red are designated respectively 20 and 21.

There are 'many advantages resulting from the use of a transparency for producing the three negative records 19, 20 and 21, in preference to producing such records by making separate exposures from the subject itself. It is a difficult v matter to make three correct exposures directly from the subject especially if there is a possi` bility of movement in the subject in which case proper registration of the colored sensation prints produced from the negatives is impossible, and in many cases the final result is most unsatisfactory.

On the other hand, by the use of a transparency this and many other difliculties are overcome. When using transparencies, there is always the possibility of correcting an over or under exposed negative of any color` by making another exposure from the original transparency or the transparency itself may be intensified or reduced either entirely or locally as may be required.

There have been numerous methods devised for making prints in the three primary or fundamental colors. Some of these methods employ the use of dyes, while some of them use pigment prints as in the carbon process, while still other methods employ a combination of both of these processes.

Those conversant with dye processes are aware of the trouble resulting from that use which causes spreading of one color into other colors, and the difficulty of registration of such prints. The carbon process which produces very beautiful results in the production of monochromatic prints is exceedingly dificult when making three delicate and infinitely fragile prints such as are required for trichrome printing. Registration of such prints when they are superposed presents an enormous difficulty owing to the chance of damage to the prints by reason of their extreme delicacy. The same remarks apply to the Carbro process which is an adaptation of the carbon process.

Attempts have been made to use tone prints, but the difficulty so far has been with the' red which is never of the required shade, always leaning strongly to a brick red Whereas as magenta red is the required tone. Bearing in mind all the foregoing troubles and difficulties. and yet realizing the possibilities of color prints, the present invention provides a method which overcomes these difficulties and makes the production of full color prints a comparatively easy matter.

The next step in the process is to print from the three negatives 19, 20 and 21 three positive sensation prints, each bearing a positive record of the amount and position of the standard trichromatic colors contained in the subject. These positive records are made upon especially prepared photographic material illustrated in Fig. 4. This material comprises a hard gelatine layer 22 in-which is incorporated a photographi-- cally sensitive silver composition, preferably silver bromide. This hard gelatine lm is secured to a backing material 23 by means of a layer 24 of relatively soft gelatine. The support 23 may be of any suitable character but is preferably a sheet of backing paper.

In Fig. 4 three sensation prints are designated generally as A, B and C. These prints are prepared by exposing for the proper period of time in contact with the negatives 19, 20 and 21 and are thereafter developedin the usual manner The next step in the process is to'secure the sensation prints A, B and Cl face downward into contact with temporary supports 25. Any suitable material may be used for these supports. A highly desirable material for this purpose is transparent celluloid. The paper prints are soaked in water and squeegeed in the contact with the celluloid sheets which-have been previously waxed and are substantially larger in area than the prints themselves which provides a convenient margin, by means of which the prints may be'more readily handled.

A very important feature of the present invention is the step in the process which permits the l gelatine lm bearing the positive images to be stripped from their original paper backing, which operation is done as follows. The threerprints mounted upon their temporary supports are subjected to a steam bath which softens the readily soluble soft gelatine layer thereby permitting the paper backing sheets 23 to be stripped from the hard gelatine films 22 without injury thereto or modification of the images contained therein.

A convenient apparatus in which to carry on this operation is shown in Figs. 6 and 7. The apparatus comprises a casing 29 secured to a bench or table and within which is received a tank 30 containing water, and beneath which is located a gas burner 31 or other suitable heating apparatus which is used to generate steam from the water contained in the tank. The steam passes upwardly through conduits` 32 and 33 at the ends of the tank. From this point the steam rises into a steam chamber 34. Above the tank 30 is situated a tray 35 xed in position and extending across the casing from one end wall to the other. Access to the tray is gained by means of hinged doors 36 and 3'7 adjacent the ends of the tray 35 and are hinged upon the casing 29 at 38. i

The steam passing through the conduits 32. and 33 is directed upward by the baffle plates 39 and 40 from where it passes along the sides of the tray 35 and upwardly into the chamber 34 in which is situated deflecting surfaces 41 which act to direct the steam downwardly into Contact with the tray.

To steam the prints one of the doors 36 is opened and a print is placed in the tray 35 and is passed out of the steam bath at the other end of the tray through the opposite door 3'7. The prints are subjected to the steam for the required length of time to soften the soft gelatine layer to the proper consistency which will permit the paper backing to be stripped from the hard gelatine layer. The stripping operation desirably is accomplished immediately upon withdrawing the prints from the steam bath. The prints` are placed in the steaming apparatus with their backing material upwardly and are subjected to the ncurrents of steam directed downwardly by the surfaces 41.

The hard gelatine films are now left adhering to their celluloid supports 25 and the silver images contained therein are ready to be converted into their respective colors. This coloring operation may be carried on before the paper backing 23 is stripped from the gelatine film. If this is done the images are colored after exposure and development, and before waxing into contact with the temporary supports. `It is preferable however to color the prints after they have been transferred to their temporary supports as at this time they are more readily handled. and the n washing operation consumes much less time.

As has been previously pointed out other methods may be used to 'col'or the prints, butthe following method-has been found to produce the most accurate and permanent reproductions.

Bleach the print which is to be converted into yellow in- Wash until all stain has disappeared, then tone in- Potassium bichromate 15 grains y3 ouncesy Water The print which is to be toned blue is placed in the following- Ammonium ferric citrate 22 grains Nitric acid 24 minims Potassium ferricyanide 45 grains Water 10 ounces The blue image must be well washed to'remove the green stain, and, if fixed in plain hypo 5% solution afterwards, a very clear transparent blue print results.

As previously stated, it is not possible to obtain a red print by toning methods, which will be in any way satisfactory but it is quite easy to convert the grey bromide into a magenta print as follows.

The celluloid, holding the print, is soaked in water and a sheet of magenta carbon tissue, cut slightly larger than the bromide print, is' sensitized in the Carbro or similar, standard baths Sodium thiosulphate 4 ounces Potassium metabisulphite l/2 ounces Water 20 ounces which removes the bleached bromide image, which would otherwise darken in daylight, and also removes any bichromate stain. After dying the three component prints are ready for assembing. Before doing so, these may be superimposed to see if the color balance is correct. When satisfied that this is so, the three color images can be assembled to make one print.

To do this av pece'of double transfer paper 42, slightly larger than the color images, is soaked in water until completely stretched.

This is then squeegeed into contact with the yellow print on celluloid and allowed to dry, or it can be subjected to a draught from an electric fan. When completely dry, the paper, with the color image, will either fall off, or can l'be peeled olf completely from' the celluloid.

"The wax, with which the celluloid was pol- .-ished, is now adhering to the surface of the yellow print, and this must be removed by absorbent cotton dipped in benzole.

The yellow print is now placed in cold water again for a few minutes and then squeegeed into contact with the red image and quickly brought into exact register. This is again dried. and removed from the celluloid support, bearing both the yellow' and red prints rmly cemented together by cohesion.4 After cleaning as before, and re-wetting, the two color print is brought into contact with the blue image when all the colors of the original will be found correct.

After drying, removing from the celluloid and cleaning, this print has now a high gloss, which is excellent for reproduction, but, if desired, this can be removed by soaking the finished print in cold water until quite limp, and allowing it to dry in the ordinary way, when the surface will be matt with a pleasant sheen. There are alternative methods, which are equally effective,

and may be preferred for some things. For instance, the bromide print, which is converted into yellow need not be transferred to celluloid, but may be used itself as the foundation print, superposing the other two colors on it.

This will give a final result of a high gloss, and, if matting is desired this must be done afterwards, but it is not necessary in this case to clean the tricolor print, as the wax on its surface ensures the matted print leaving the surface of the ground opal glass (which is best for this purpose) easily.

Another variation is to make all three grey images or their celluloids into color images, by using carbon tricolor tissues for each in the same Way as for the red previously.

In this way, however, the yellow print cannot be used for the final support, unless it is well hardened and thoroughly washed before conversion into its yellow state.

A still further variation is to convert the grey lbromide prints on the celluloids into dye images but as before mentioned this is not recommended.

In all methods of color printing, in which celluloid sheets are used for the temporary supports, it is of undoubted advantage to use a substratum to secure perfect holding of the delicate detail of the color images, but, with the method just described, no substratum is needed, as the film of hardened gelatine acts in the desired way itself. l

The three superposed colored films may themselves be used as a transparency, to be viewed by transmitted light or they may be mounted upon a piece of glassror other transparent material 42 to provide mechanical support for the films.

It is more desirable, however, that the films be mounted upon a support having a substantially totally refiecting surface. Such reflecting surface may be pure white or may contain a light tint of a particular color which it is desired to introduce into the reproduction to obtain a desired special effect. For instance, While it is possible to reproduce a subject correctly by the above method, it may be desirable in some cases such as in a snow scene to overemphasize the blue or in views of another character such as a landscape in summer, a green tint may be thus introduced. This may be done by mounting the films upon a support having the blue or the green tint.

Another possibility of controlling the impression created by the reproduction is to use upon the reflecting surface a color compensatory of the variation from daylight of that of the color source which is projected upon the reproduction.

Having thus described the invention, what is claimed as new, and desiredto be secured by Letters Patent, is:

1. The method of making photographic reproductions in colors consisting in making two or more photographic records, each bearing a negative image representing the amount and position of a fundamental color as contained. in the subject, making two or more sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying a photographically sensitive silver composition and a relatively soft layer adherent to a support, each print bearing a positive silver image of its respective color, causing each of the gelatine films to adhere to a transparent temporary support, softening the layer of gelatine adhering to each origilcolor, causing each of the gelatine films to adnal support, stripping the original support from each of the gelatine .films in the presence of steam, converting' each positive image to -that color it is to create in the finished reproduction, superposing the films and securing in registered position by cohesion, each temporary backing being removed from its respective film after each lso superposition.

9.5 here to a transparent temporary support, softening the layer of gelatine adhering to the original support of each of the gelatine films in the. presence of steam, converting each positive image to that color it is to create in the finished 190 reproduction superposing each film in the registered position with its soft gelatine layer in a softened tacky condition thereby securing the films in such position by cohesion, each temporary backing being removed after each superposition.

3. The method of making photographic reproductions in colors consisting in' making tWo or more photographic records, each record bearing a negative image representing the amount and position of a fundamental color as contained in the subject making two or more sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying a photographically sensitive silver composition and 1 15 a relatively soft layer adherent to a paper support, each print bearing a positive silver image of its respective color, causing each of the gelatine films to adhere to a transparent temporary support, softening the layer of gelatine adhering 1,20 to each paper support by subjecting it to the action of steam, stripping the original supports from each of the gelatine films, converting each positive image to that color it is to create in the finished reproduction superposing the films and securing in registered position by cohesion, each temporary backing being removed from its respective film after each superposition and mounting the superposed films upon a support having a substantially totally reflecting surface.

4. The method of making photographic reproductions in colors consisting in making two or more photographic records upon panchromatically sensitized photographic material by means of appropriate colored filters, each record bearing a negative image representing the amount and position of a fundamental color asl-contained in the subject making two or more sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying a lphotographically sensitive silver composition and but one of the positive images to that color it is to create in the nished reproduction, superposing the films and securing in registered position by cohesion each temporary backing being removed from its respective lm after each superposition.

5. The method of producing a photographic reproduction in natural colors consisting in making a transparency in natural colors by a photographic process contact printing three or more negative records .from `the transparency rrby inserting in the path of :a light source suitable colored filters, each negative record representing the amountand position of one of the fundamental colors contained in the transparency making sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying a photographically sensitive silver composition and a relatively soft layer adherent to a support, each print bearing a positive silver image of its respective color, causing each of the gelatine films to adhere to a transparent temporary support softening the layer of gelatine adhering to each original support by subjecting it to the action of steam, stripping the original supports from each of the gelatine films converting each positive image to that color it is to create in the finished reproduction, superposing the films and securing in registered position by cohesion, each temporary backing being removed from its respective lm after each superposition.

6. The method of making photographic reproductions in natural colors comprising the steps defined in claim 5 together with mounting the superposed gelatine lms upon a support having a surface which is substantially totally reflecting.

7. The method of making photographic reproductions in natural colors consisting in making three or more photographic records, each record bearing a negative image representing the amount or position of a fundamental color as contained in the subject making two or more sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying 'a photographically sensitive silver composition and a relatively soft layer adherent to a paper support, each print bearing a positive silver image of its respective color causing all but one of the gelatine films to adhere to a transparent temporary support, softening the layer of gelatine adhering to each paper support by subjecting it to the action of steam stripping the paper supports from each of the gelatine films with the exception of the film not transferred to a temporary support, converting each of the positive images to that color it is to create in the finished reproduction, superposing the films which are mounted on temporary supports and securing them in registered position by cohesion upon the film which is still attached to its original paper support, the temporary backing upon each of those films so superposed being removed from its respective lrn after each superposition.

8. The method of producing photographic reproductions in natural colors consisting in making three or more photographic records, each it to the action of steam, stripping the original record bearing a negative image representing the amount and position of a fundamental color as contained in the subject, making two or more sensation positive prints from the negatives upon a gelatine emulsion having a hard layer carrying a. photographically sensitive silver composition and a relatively soft layer adherent to a support, each print bearing a positive silver image of its respective color, converting each positive image to that fundamental color it is to create in the finished reproduction, causing each of the gelatine lms to adhere to a transparent temporary support softening the layer of gelatine adhering to each of the original supports by subjecting supports from each of the gelatine lms, superposing the lms and securing in registered position by cohesion, each temporary backing being removed from its respective yfilm after each superposition.

9. The method of making photographic re-v productions in natural colors comprising the steps defined in claim 8 together with mounting the superposed gelatine lms upon a transparent support permitting the reproductionoto be viewed by transmitted light.

10. The method of making photographic reproductions in natural colors comprising the steps deiined in claim 8 together with mounting the superposed gelatine iilms upon a support having a surface which is substantially totally reflecting.

11. Steps in the process of producing photographic reproductions in natural colors which consists in producing a lm which comprises a gelatine emulsion having a hard layer carrying a photographically sensitized silver composition and a relatively Asoft gelatine layer adherent to a support making a. photographic record upon said sensitized layer releasing said hard layer from said support by the action of steam upon said soft gelatine layer.

l2. Steps in the process of producing photographic reproductions in color which consists in printing a positive image representing the amount and position of a fundamental color of the subject upon a gelatine emulsion having a hard layer carrying a photographically sensitive composition and a relatively soft layer adherent to a support, releasing said hard layer from said support by the action of steam upon said soft gelatine layer.

13. Steps in the process of making photographic reproductions in colors which consist in printing a positive image representing the amount-and position of a dierent primary color of the subject upon each of a plurality of gelatine emulsions, each emulsion having a hard layer carrying a photographically sensitive composition and a relatively soft layer adherent to a paper backing, releasing said hard layer from said paper backing by the action of steam upon said soft gelatine layer and superposing said layers of hard gelatine emulsions with their imagesl in registry while the soft gelatine layer remaining upon the hard layer is still in a tacky condition. 14g

LEONARD G. NICOLL. 

